I'm sure by now everyone has heard the old adage 'Eyebrows should be sisters, and not twins'...but what if you want your brows to be twins, dammit?! I hate to break it to ya, but even twins don't look exactly the same, ha! You can get pretty darn close though, I promise. Here's my best advice:
If you have been shaping your own brows, it might be time to seek professional help. Sometimes growing your brows out for a few months (I'd recommend using a brow serum like this for max re-growth) and then having them shaped professionally can bring back more symmetry. It's easy to lose perspective and over-tweeze or not maintain a uniform shape when you are always doing them yourself.
The next thing to consider is how to fill your brows in to make them match. The first step to achieving this is to map them out using what brow Wizardess Anastasia (of Anastasia Beverly Hills fame) calls the 'Golden Ratio'.
Use a brow pencil or brow powder to mark three points on your brow. The beginning of your brow should be in a straight line up from the center of your nostril. The highest point, aka the arch of your brow, should be in line with the tip of your nose as the line runs through the pupil. The tail end of your brow should be in line from the outer corner of your nostril and the outer corner of your eye.
Once you have made marks on both of your brows, you have a much better way to visually see where your brows are falling short on each side as far as their ideal shape goes. The next thing to consider is where your brows lie on the horizontal axis—meaning which points rest higher or lower on the face from side to side. This is most women's biggest challenge! Luckily, having those three Golden Ratio anchor points will allow you to see the difference a bit more clearly. To make your brows match, I recommend filling them in in three sections (beginning, middle/arch, and tail), going back and forth between your two brows as you do each section. Start with the beginning of your brow. If one brow begins a little higher in this area, consider filling in more on the underside to bring it down to match the level of your other brow. You may need to also fill more on the top side of the brow that is lower to help level them out. Do what makes the most sense for your brows. You can do this! Continue this process as you go through the rest of the brow. Because you are looking back and forth between your brows one section at a time you are able to see the differences more clearly, and adjust on each side as necessary. It's waaaay easier than filling in each brow completely and then trying to spot the differences. Just remember to fill your brows in using very light-handed, hair like strokes (see our tutorial on how to fill in your brows naturally if you want a demo).
Once you have done this process several times and memorized what areas of your brow need to be filled in differently, you will most likely be able to abandon the mapping process and fill them in by eye. For instance, on my own brows I automatically know I need to fill underneath the middle portion of my right brow and fill in the top side at the arch and tail end of both brows to make them look their best. Once you learn your brows, this process becomes second nature!